Nowadays, Ni-based superalloys are widely used as high-temperature structural materials for turbine parts of jet engines and gas turbines, etc. The Ni-based superalloys contain metallic phases (γ) exceeding a volume fraction of above 35 vol. % as a constituent phase, and consequently have limitations in melting point and high-temperature creep strength. Intermetallic compounds showing a positive temperature dependence of yield stress are promising materials as the high-temperature structural materials superior to the conventional Ni-based superalloys. However, monolithic intermetallic compounds have drawbacks of poor ductility at ambient temperature and also low creep strength at high temperature. Ni3X type intermetallic compounds have a GCP (geometrically closed packaged) crystal structure, and some of such compounds may be used in combination with high coherency. Many of the Ni3X type intermetallic compounds have excellent properties. Therefore, by using the Ni3X type intermetallic compounds, a new type of multi-phase intermetallic compounds (multi-phase intermetallics) having further excellent properties and a high freedom for microstructural control are expected to be produced.
An attempt has been made to develop a multi-phase intermetallic compound composed of Ni3Al(L12)-Ni3Ti(D024)-Ni3Nb(D0a) system, and it was found that an alloy having excellent properties can be developed (see Non-Patent Document 1).    Non-Patent Document 1: K. Tomihisa, Y. Kaneno, T. Takasugi, Intermetallics, 10 (2002)247